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[heap] Remove unnecessary length reloading from ArrayList::Add.

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The reloading was needed when GC would compact the Heap::retained_maps
array. But that's no longer true; the compaction is done in
Heap::AddRetainedMap, outside GC. So it's not possible that the length would
change because of an allocation.

(Pre-cleanup for in-place weak ref work.)

BUG=v8:7308

Change-Id: I18554353014865992f9151002cc4097fb986faf1
Reviewed-on: https://chromium-review.googlesource.com/1002775
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52506}
This commit is contained in:
Marja Hölttä 2018-04-09 16:58:53 +02:00 committed by Commit Bot
parent bbb26b5f75
commit 89f5bf7fde
4 changed files with 9 additions and 42 deletions
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3
src/heap/heap.cc
View File

@ -5018,8 +5018,7 @@ void Heap::AddRetainedMap(Handle<Map> map) {
CompactRetainedMaps(*array);
}
array = ArrayList::Add(
array, cell, handle(Smi::FromInt(FLAG_retain_maps_for_n_gc), isolate()),
ArrayList::kReloadLengthAfterAllocation);
array, cell, handle(Smi::FromInt(FLAG_retain_maps_for_n_gc), isolate()));
if (*array != retained_maps()) {
set_retained_maps(*array);
}

16
src/objects.cc
View File

@ -10275,14 +10275,11 @@ Handle<FixedArrayOfWeakCells> FixedArrayOfWeakCells::Allocate(
}
// static
Handle<ArrayList> ArrayList::Add(Handle<ArrayList> array, Handle<Object> obj,
AddMode mode) {
Handle<ArrayList> ArrayList::Add(Handle<ArrayList> array, Handle<Object> obj) {
int length = array->Length();
array = EnsureSpace(array, length + 1);
if (mode == kReloadLengthAfterAllocation) {
DCHECK(array->Length() <= length);
length = array->Length();
}
// Check that GC didn't remove elements from the array.
DCHECK_EQ(array->Length(), length);
array->Set(length, *obj);
array->SetLength(length + 1);
return array;
@ -10290,12 +10287,11 @@ Handle<ArrayList> ArrayList::Add(Handle<ArrayList> array, Handle<Object> obj,
// static
Handle<ArrayList> ArrayList::Add(Handle<ArrayList> array, Handle<Object> obj1,
Handle<Object> obj2, AddMode mode) {
Handle<Object> obj2) {
int length = array->Length();
array = EnsureSpace(array, length + 2);
if (mode == kReloadLengthAfterAllocation) {
length = array->Length();
}
// Check that GC didn't remove elements from the array.
DCHECK_EQ(array->Length(), length);
array->Set(length, *obj1);
array->Set(length + 1, *obj2);
array->SetLength(length + 2);

10
src/objects/fixed-array.h
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@ -372,15 +372,9 @@ class FixedArrayOfWeakCells : public FixedArray {
// underlying FixedArray starting at kFirstIndex.
class ArrayList : public FixedArray {
public:
enum AddMode {
kNone,
// Use this if GC can delete elements from the array.
kReloadLengthAfterAllocation,
};
static Handle<ArrayList> Add(Handle<ArrayList> array, Handle<Object> obj,
AddMode mode = kNone);
static Handle<ArrayList> Add(Handle<ArrayList> array, Handle<Object> obj);
static Handle<ArrayList> Add(Handle<ArrayList> array, Handle<Object> obj1,
Handle<Object> obj2, AddMode = kNone);
Handle<Object> obj2);
static Handle<ArrayList> New(Isolate* isolate, int size);
// Returns the number of elements in the list, not the allocated size, which

22
test/cctest/heap/test-heap.cc
View File

@ -4658,28 +4658,6 @@ TEST(MapRetaining) {
CheckMapRetainingFor(7);
}
TEST(RegressArrayListGC) {
FLAG_retain_maps_for_n_gc = 1;
FLAG_incremental_marking = 0;
FLAG_gc_global = true;
CcTest::InitializeVM();
v8::HandleScope scope(CcTest::isolate());
Isolate* isolate = CcTest::i_isolate();
Heap* heap = isolate->heap();
AddRetainedMap(isolate, heap);
Handle<Map> map = Map::Create(isolate, 1);
CcTest::CollectGarbage(OLD_SPACE);
// Force GC in old space on next addition of retained map.
Map::WeakCellForMap(map);
heap::SimulateFullSpace(CcTest::heap()->new_space());
for (int i = 0; i < 10; i++) {
heap->AddRetainedMap(map);
}
CcTest::CollectGarbage(OLD_SPACE);
}
TEST(WritableVsImmortalRoots) {
for (int i = 0; i < Heap::kStrongRootListLength; ++i) {
Heap::RootListIndex root_index = static_cast<Heap::RootListIndex>(i);